Fuel for high pressure liquid fuel injection engines



Patented June 30, 1936 UNITED STATES FUEL roa moi! PRESSURE LIQUID FUEL mmo'rron aromas George M. Maverick, Elizabeth, N. 1., assignor to Standard Oil Development Company, a corporation of Delaware No Drawing. Application July 11, 1933,

Serial No. 679,891

1 Claim. (01. 44-9) This invention relates to improved fuels for en- 7 gines employing high pressure liquid fuel injection, such as the Diesel and spark ignited types,

and 'more particularly it relates to such fuels con-.

taining extreme-pressure lubricating ingredients and also'to methods of producing such fuels.

There have been many attempts to develop high-speed Diesel engines for various, particular uses such as automotive, aviation, railroad or sta- 10 tionary use, but these have not been attendedwith the desired degree of success. This partial failure is, to a certain extent, due to the inability to use sufliciently low viscosity fuels as they are deficient in lubricating valuewith the result that fuel pumps and injection valves fail after a short period of operation. It is an object of the present invention to overcome these difficulties.

Internal combustion engines are of two general types: those employing the Otto cycle as in the ordinary automobiles and those of the auto-ignition type which use the Diesel cycle. The principal difference between these two types is that in the Otto cycle, air and fuel are mixed in a carburetor and the mixture isadmitted to the cylinder, compressed by the piston to between 50 and.-

225 pounds per square inch and then ignited by an electric spark; whereas in the Diesel cycle, air alone is first admitted to the cylinder and compressed to a much higher pressure, 1. e., between 500 and 2,000 pounds per square inch, andthen liquid fuel is injected and the mixture automatically ignites due to the increased temperature which resulted from the high compression of the air.

It is therefore apparent that in using the Diesel cycle the liquid fuel must be injected under pressures sufficiently high to overcome the pressure of the'compressed air already in the cylinder. Under these conditions, it is difllcult to lubri- 40 cate the'fuel injection pumps, valves and nozzles.

However, for ordinary Diesel operation, it is desirable to use a fuel of as low a viscosity as possible. There are many reasons for this selection, the most important being that better injection is obtained, and that the auto-ignition temperature is lower. Unfortunately, petroleum fuels of such low viscosities have substantially little lubricating value, and since the fuel in most engines of this type is also the lubricant for the injection pumps and valves, it has been found necessary to employ oils of viscosities sufliciently high to give the desired lubrication. However, due to such high viscosity, injection of this fuel through the nozzle toproduce the most eflicient spray is dim- 5 cult, and engines of this type suffer through improper atomization and combustion, too high auto-ignition temperature (A. I. T.),, difficult starting, waste of fuel, etc. 4

This invention involvesthe elimination of such difllculties in not only the true Diesel type of auto- 5 ignition engines, but also in the other modified prime movers such as the Hesselman and Atlas engines which employ the Otto cycle involving liquid fuel injection and spark ignition.

' Broadly, the invention consists in addingto the 10 fuel certain materials which will increase its lubricity though without appreciably increasing its viscosity or having any other harmful effects. These materials are generally termed extreme pressure lubricants or load carrying agents and 15 their important'characteristic consists in the fact that only small amounts need be added to the fuel to increase its oiliness to the desired extent.

' In this respect'they differ from the mineral oils which owe their lubr cating powers mainly to 20 their viscosity. Generally, from to 2% is sufficient, although the actual amount added depends upon the materials blended. Suitable materials to be added include reactive sulfur compounds, alone or with tin and lead compounds. 25

Certain organic acids and esters may also -be used. The acids should be of the naphthenic ac d type, and usually should comprise molecules containing 8 to 10 carbon atoms or preferably more.

' The esters should have a relatively high boiling '30 point, that is, in the range of or above the temperature of the combustion chamber. Such high-boiling esters may be of the cyclic, heterocyclic, aliphatic or mixed types. Esters having a boiling point above C., claimed in co-pend- 35 mg application SerQNo. 600,828 by Per K. Frolich, include inter alia amyl butyrate (B. Pt. 176 C.), butyl naphthenate, phenyl acetate (B. Pt. 196 C.'), etc. Still higher boiling esters are claimed in co-pending application Ser. No. 667,039, filed 40 April 20, 1933, by Jones I. Wasson, as a gum flux or upper cylinder lubricant in a motor fuel; some of the specific esters'disclosed are amyl and heptyl stearate, amyl cinnamate (B. Pt. 572 F.) and secondary amyl ester of mono-toluene stearic-i5 acid (B. Pt. between 700-800 F.) Such compounds must have sufliciently high boiling points so as not to boil 011 at the temperature of the cylinder head. Furthermore, they must be sufllciently stable so as not to decompose to insoluble 50 products, thereby causing clogging of the injection nozzle.

Substances comprising sulfur should be sumciently unstable to be of the active or corrosive type, since otherwise, little if any increase in 56 lubricity is obtained. In preparing sulfur compounds, sulfur may be cooked with paraffin wax used, for example, a mixture such as sulfurined fuel such as benzol, alcohol,etc. A special gasooil and lead oleate; and also mixtures of any such ingredients with some of the organic acid and ester type mentioned above may be used. In this way a superior lubricating property is imparted to the fuel with which those ingredients are mixed. Specific examples of various illustrative combinationswill be given hereinafter.

The fuel to be used 'may be a single type petroleum hydrocarbon fuel such as gas oil, kerosene or gasoline, or may be a blended fuel comprising petroleum hydrocarbons as well as other types of line type fuel, known as safety fuel, is particularly useful in the present invention. This safety fuel which is claimed separately in co-pending application Ser. No. 464,450 by F. A. Howard has a boiling range between theapproximate limits of 300 to 550 F. Its chief advantage lies in the. absence of the very low boiling ends which are apt to create a: fire hazard. Such a specially cut naphtha, free from both light andheavy ends, may consist either of the hydrocarbons normally present in ordinary gasoline or a cracked gasoline or may preferably be produced by hydrogenation of various types of hydrocarbons as is more fully described in the Howard application referred to.

Likewise, instead of using the usual Diesel fuels which generally have gravities of 26 to 30 A. P. I. and viscosities in the neighborhood of 50 seconds Saybolt, it is possible to employ fuels of to A. P. I. gravity and 300 to 450 refined oil viscosity (30 to 35 Saybolt).

the invention, the additionagentis addedto the fuel base in amounts varying generally from 0.1% up to 5.0% or so, depending upon the type of fuel and addition agents as well as the design of the high pressure injection engine in which the fuel will be burned. Generally, with the heavier types of fuel, only a small amount of load, carrying agent is necessary, whereas with the lighter hy- In preparing the improved fuels according to drocarbon fuels of the gasoline type a larger amount of addition agent will be required. These addition agents may either be added directly to the large bulb of fuel base or they may be incor-' porated into a small amount of the fuel base and then this mixture stirred into the larger bulk of the'fuel -base.

For-the sake There may also be added to these auto-ignition engine fuels any other substances desired, for example, materials adapted to facilitate the ignition of the fuel, such as nitro compounds, knock inducers, dyes, inhibitors, or gum fluxes such as the high-boiling mineral oil of naphthenic type as disclosed in the co-pending application of Sloane and Wasson, Ser; No. 658,153 filed February 23, 1933.

In the appended claims the expressions a fuel for high pressure liquid fuel injection engines and a Diesel fuel" are intended to mean fuels having a sufilcient lubricity or load carrying capacity that they are adapted to prevent excessive wear of fuel injection pumps and other moving parts in contact with the fuel under the high pressures used in such engines.

It is-not intended that the invention be limited to the specific examples given nor to any theory of the operation of the invention but it is desired to claim broadly all inherent novelty in the invention.

and containing 0.5 to 5.0% of a compound containing a substantial amount of chemically combined sulfur in a reactive condition, said fuel also containing-about 0.5 to 2.0% of a compound of a metal of the group consisting of tin and lead,

of illustration only and without which compound is capable of reacting with the.

sulfur compound to give increased lubricity.

GEORGE M. MAVERICK. 

